As video transmission systems have matured, digital video is more readily available via a variety of different communications systems and networks. Specifically, digital video, such as television programs, can be transmitted as multicast digital bit streams of video signals to users over networks. Multicast digital bit streams typically include digital video frames. A predetermined number of frames is conventionally referred to as a Group of Pictures (GOP). The GOP lengths are typically 15 or 30 frames. With more advanced video formats, such as Advanced Video Coding (AVC) and/or Windows Media 9 (WM9), the GOP length can be substantially longer in order to reduce the bit rate.
In order to reduce costs and simplify the amount of effort associated with video transmission, different video compression/de-compression techniques have been developed and established. Some of the better known and more widely adopted video compression/de-compression standards include Motion Picture Experts Group 2 (MPEG-2) data streams and Motion Picture Experts Group 4 (MPEG-4) data streams. Hence, television programs are often transmitted over the network as Motion Picture Experts Group 2 (MPEG-2) data streams or Motion Picture Experts Group 4 (MPEG-4) data streams. Conventionally, for purposes of video compression/decompression, a video stream is processed one frame at a time.
Compressed video transmission streams typically include a variety of different compression frame types. With MPEG-2 and MPEG-4, the bit streams generally include three different types of frames including Intra-frames, Predictive frames, and Bidirectional interpolated frames. In a typical decoding process, Intra-frames (I-frames) can be decoded independently without the need of referencing another frame. Thus, GOPs typically start with an I-frame. Predictive frames (P-frames) can be decoded by referencing a previous I-frame or P-frame. Bidirectional interpolated frames (B-frames) can be predicted from a previous and a following P-frame or I-frame. For a given video stream, all three ways of coding are attempted and the best and most efficient combination is utilized. For example, a common MPEG-2 video stream can be 15 frames long and have the sequence IBBPBBPBBPBBPBB.
Typically, a video stream, such as a MPEG-2 data stream, is transmitted from a multicast source to a router and/or switch via a network, e.g., an Internet Protocol (IP) distribution network. And upon receipt of the video stream, the router then transmits the video stream to a user device, such as a set-top box. Such a router (e.g., the user's Internet gateway) can potentially receive multiple multicast video streams at one time (e.g., one or more streams for each of a plurality of video channels), and client devices (e.g., dedicated streaming devices such as the set-top box, mobile devices, tablet devices, etc.) can request specific streams to be output for display.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.